Messages in this thread | | | Date | Tue, 13 Jun 2017 10:30:43 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH v6 00/18] mtd: nand: denali: Denali NAND IP patch bomb |
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On Tue, 13 Jun 2017 17:17:41 +0900 Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
> Hi Boris, > > > 2017-06-13 16:02 GMT+09:00 Boris Brezillon <boris.brezillon@free-electrons.com>: > > > > > BTW, I also implemented ->read/write_buf_word() since the core may one > > day call these functions, and the default implementations used by the > > core when these hooks are NULL are not appropriate in your case. > > > > BTW, why doesn't the default hook in the core do like this? > > > static uint8_t nand_read_byte(struct mtd_info *mtd) > { > struct nand_chip *chip = mtd_to_nand(mtd); > uint8_t byte; > > chip->read_buf(chip, &byte, 1); > return byte; > } > > > ->read_byte() is a special case of ->read_buf() with length==1, > so this should work.
Not sure it works for all implementation. ->read_byte() is expected to return the lower 8 bits when interacting with a 16-bits bus. If we do what you suggest, and ->read_buf() appears to be caching data in an intermediate buffer if the amount of data is not aligned on 2 bytes, you might retrieve data you don't care about when ->read_byte() is called several times.
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